Driving assistance system, driving assistance method, and driving assistance program

Abstract

Provided is a driving assistance system, which has (a) processor(s) to assist in avoiding a collision with a physical entity during driving of a host vehicle. At least one processor of the driving assistance system is configured to execute: planning a driving trajectory (Td) of the host vehicle; and adjusting a front wheel steering angle (δf) and a rear wheel steering angle (δr) imparted from a steering actuator to a front wheel part and a rear wheel part, respectively, in the host vehicle to be in phase with a reference longitudinal direction (X), thereby controlling a braking posture of the host vehicle in accordance with the driving trajectory (Td) during an avoidance control period (Pc) for collision avoidance.

Description

Driving support system, driving support method, driving support program Cross-reference to related applications

[0001] This application is based on Japanese Patent Application No. 2024-161324 filed in Japan on September 18, 2024, and the contents of the base application are incorporated herein by reference in their entirety.

[0002] The present disclosure relates to a driving support technology for assisting in avoiding collisions with objects in vehicle driving.

[0003] In the driving support technology disclosed in Patent Document 1, as the braking posture of the host vehicle is swivel-controlled to avoid a collision between the vehicle and an object, the rear-wheel steering angle is adjusted in the opposite phase to the swivel direction, thereby increasing the lateral movement amount of the vehicle.

[0004] Japanese Patent No. 5988171

[0005] However, in the case of the driving support technology disclosed in Patent Document 1, since the braking force in the front-rear direction for collision avoidance is increased and controlled in the vehicle, the tire lateral force that can be generated by the rear-wheel steering angle becomes insufficient within the friction circle between the tire and the road surface. As a result, there was a concern that it would interfere with the actual increase in the lateral movement amount of the host vehicle.

[0006] An object of the present disclosure is to provide a driving support system effective for avoiding collisions with objects in a vehicle. Another object of the present disclosure is to provide a driving support method effective for avoiding collisions with objects in a vehicle. Yet another object of the present disclosure is to provide a driving support program effective for avoiding collisions with objects in a vehicle.

[0007] Hereinafter, the technical means of the present disclosure for solving the problems will be described.

[0008] A first aspect of the present disclosure is a driver assistance system having at least one processor for assisting collision avoidance with a target during the driving of a host vehicle, wherein the at least one processor is configured to plan the driving trajectory of the host vehicle and to control the braking posture of the host vehicle in accordance with the driving trajectory during the avoidance control period toward collision avoidance by adjusting the front wheel steering angle and rear wheel steering angle applied to the front wheel section and rear wheel section, respectively, from steering actuators in the host vehicle to be in phase with respect to a reference longitudinal direction.

[0009] A second aspect of the present disclosure is a driving assistance method performed by at least one processor to assist in avoiding a collision with a target during the driving of a host vehicle, comprising: planning the driving trajectory of the host vehicle; and controlling the braking posture of the host vehicle in accordance with the driving trajectory during the avoidance control period toward collision avoidance by adjusting the front wheel steering angle and rear wheel steering angle applied to the front wheel section and rear wheel section, respectively, from steering actuators in the host vehicle to be in phase with respect to a reference longitudinal direction.

[0010] A third aspect of the present disclosure is a driving assistance program stored in at least one storage medium for assisting collision avoidance with a target in the driving of a host vehicle, and including instructions for causing at least one processor to perform collision avoidance assistance, the program including instructions for planning the driving trajectory of the host vehicle and for controlling the braking posture of the host vehicle in accordance with the driving trajectory during the avoidance control period toward collision avoidance by adjusting the front wheel steering angle and rear wheel steering angle applied to the front wheel section and rear wheel section, respectively, from steering actuators in the host vehicle to be in phase with respect to a reference longitudinal direction.

[0011] According to these first to third embodiments, the front wheel steering angle and rear wheel steering angle applied to the front and rear wheel sections of the host vehicle by steering actuators are adjusted in phase with respect to the reference longitudinal direction. This allows the host vehicle to transition its braking posture in the direction of travel of the front and rear wheels in accordance with the planned driving trajectory during the avoidance control period for collision avoidance with a target. Therefore, it becomes possible to secure an effective amount of lateral movement for collision avoidance in the host vehicle.

[0012] This is a block diagram showing the physical configuration of the driver assistance system according to the first embodiment. This is a schematic diagram showing the driving environment of the host vehicle to which the first embodiment is applied. This is a block diagram showing the functional configuration of the driver assistance system according to the first embodiment. This is a schematic diagram for explaining the driver assistance according to the first embodiment. This is a graph for explaining the driver assistance according to the first embodiment. This is a flowchart second embodiment. This is a flowchart for explaining the driver assistance according to the third embodiment. This is a graph for explaining the driver assistance according to the third embodiment.

[0013] Hereinafter, several embodiments of this disclosure will be described with reference to the drawings. In each embodiment, the same reference numerals will be used for corresponding components, and redundant explanations may be omitted. Furthermore, if only a part of the configuration is described in each embodiment, the configuration of other embodiments described earlier may be applied to the other parts of that configuration. Moreover, not only the combinations of configurations explicitly stated in the description of each embodiment, but also the configurations of multiple embodiments may be partially combined even if not explicitly stated, as long as there are no particular problems with the combination.

[0014] (First Embodiment) The driver assistance system 1 of the first embodiment shown in Figure 1 assists in the driving of a host vehicle 2. At least a part of the driver assistance system 1 is installed in the host vehicle 2. The host vehicle 2 to which the driver assistance system 1 is applied should preferably be capable of realizing an automated driving level, such as one defined in SAE J3016, where an automated driving task exists along with a manual driving task to support the operator's manual driving. Such a host vehicle 2 is, for example, a road user such as an automobile, truck, or bus, and may be referred to as an ego-vehicle. As described above, the driver assistance system 1 targets a driver who is aboard the host vehicle 2 and capable of manual driving as the target of driver assistance.

[0015] As shown in Figure 2, in the driving environment on which the host vehicle 2 operates, a traffic scene is assumed in which at least one type of object 3 other than the host vehicle 2 exists, such as other road users and structures. Other road users include vulnerable road users and non-vulnerable road users, depending on their degree of vulnerability. Vulnerable users are, for example, people such as pedestrians. Non-vulnerable road users are, for example, at least one type of vehicle from among automobiles, trucks, buses, motorcycles, and bicycles that has a person as an occupant.

[0016] As shown in Figures 1 and 3, the host vehicle 2 is equipped with at least a portion of the driver assistance system 1, including the actuator system 4, sensor system 5, communication system 6, map database (DB) 7, and information display system 8. However, Figure 1 shows a representative example in which the entire driver assistance system 1 is mounted on the host vehicle 2, as an example of implementation in the form of a control device (e.g., control circuit) or semiconductor device (e.g., semiconductor chip).

[0017] The actuator system 4 is configured to control the driving behavior of the host vehicle 2 based on control commands from the driver assistance system 1. The actuator system 4 includes at least one type of powertrain actuator 40, such as an internal combustion engine and a motor-generator motor. The actuator system 4 includes at least one type of steering actuator 42, such as a power steering unit. The actuator system 4 includes at least one type of braking actuator 44, such as a brake unit.

[0018] As shown in Figure 2, the host vehicle 2 is equipped with left and right front wheel sections 20fl, 20fr and left and right rear wheel sections 20rl, 20rr. The steering actuator 42 adjusts the steering angles applied to the host vehicle 2 independently by motor torque, as shown in Figures 4 and 5, the front wheel steering angle δf which is common to the left and right front wheel sections 20fl, 20fr and the rear wheel steering angle δr which is common to the left and right rear wheel sections 20rl, 20rr. This allows the phase relationship between the front wheel steering angle δf and the rear wheel steering angle δr to be controlled in the host vehicle 2. The front wheel steering angle δf and the rear wheel steering angle δr are defined such that, with a phase angle of 0° in the reference vertical direction X, the counterclockwise direction around the yaw axis in the host vehicle 2 as the positive direction and the clockwise direction as the negative direction (or the exact opposite direction relationship).

[0019] Here, as shown in Figure 4, the reference longitudinal direction X is assumed to be the forward direction, specifically the longitudinal direction of the host vehicle 2 in a top view. Therefore, for the phase relationship between the front wheel steering angle δf and the rear wheel steering angle δr to be adjusted to be in phase with respect to the reference longitudinal direction X, it is sufficient that the signs of the steering angles δf and δr match, and the magnitudes of the steering angles δf and δr may be the same or different. On the other hand, for the phase relationship between the front wheel steering angle δf and the rear wheel steering angle δr to be adjusted to be out of phase with respect to the reference longitudinal direction X, it is sufficient that the signs of the steering angles δf and δr differ.

[0020] The braking actuator 44 independently adjusts, by hydraulic pressure, the braking force applied to the host vehicle 2, as shown in Figures 4 and 5, by providing individual front wheel braking forces Ff to each front wheel section 20fl, 20fr and individual rear wheel braking forces Fr to each rear wheel section 20rl, 20rr. This allows the host vehicle 2 to control the left-right and front-rear distribution of braking force. Here, the magnitude of the front wheel braking force Ff may be the same or different between the left and right wheels. Similarly, the magnitude of the rear wheel braking force Fr may be the same or different between the left and right wheels. Furthermore, the magnitudes of the front wheel braking force Ff and the rear wheel braking force Fr may be the same between at least one of each on the left and right sides, or they may be different between all of them. The front wheel braking force Ff and the rear wheel braking force Fr are defined such that the reverse direction opposite to the reference longitudinal direction X is set as the negative direction (or the exact opposite directional relationship) in the host vehicle 2.

[0021] The braking actuator 44 may be equipped with an ABS (anti-lock brake system) control function so as to be able to adjust the front wheel braking force Ff and the rear wheel braking force Fr according to the respective slip ratios of the front wheel sections 20fl, 20fr and the rear wheel sections 20rl, 20rr. The front wheel braking force Ff and the rear wheel braking force Fr may be generated using regenerative braking in a powertrain actuator 40, such as a drive motor. In this case, by equipping the powertrain actuator 40 with an ABS control function, the braking force of the regenerative brake of the drive motor may be adjusted according to each slip ratio.

[0022] The sensor system 5 shown in Figures 1 and 3 acquires sensing information usable by the driver assistance system 1 by sensing the external and internal environments of the host vehicle 2. For this purpose, the sensor system 5 includes an external sensor 50 and an internal sensor 52. The external sensor 50 may sense targets 3 present in the external environment of the host vehicle 2. The target-sensing type external sensor 50 is at least one of the following: a camera, LiDAR (light detection and ranging / laser imaging detection and ranging), a millimeter-wave sensor, and a sonar sensor. Multiple types of target-sensing type external sensors 50 are preferably implemented in combination so that they can sense in the front, side, and rear directions of the host vehicle 2.

[0023] The internal environment sensor 52 may sense specific kinetic physical quantities related to vehicle motion within the internal environment of the host vehicle 2. The motion-sensing type internal environment sensor 52 is at least one of the following: a speed sensor, an acceleration sensor, a gyro sensor, and an inertia sensor. The internal environment sensor 52 may also sense the actions or states of occupants, including the driver, as passengers in the internal environment of the host vehicle 2. The occupant-sensing type internal environment sensor 52 is at least one of the following: an accelerator pedal sensor, a steering angle sensor, a steering torque sensor, a brake pedal sensor, a shift sensor, an occupant camera, a heart rate sensor, and a steering switch.

[0024] The communication system 6 acquires communication information usable by the driver assistance system 1 via a communication network. The communication system 6 may receive positioning signals from GNSS (global navigation satellite system) satellites located outside the host vehicle 2. A positioning-type communication system 6 is, for example, a GNSS receiver. The communication system 6 may send and receive communication signals with a V2X system located outside the host vehicle 2. A V2X communication-type communication system 6 is, for example, at least one of a DSRC (dedicated short range communications) communication device and a cellular V2X (C-V2X) communication device. The communication system 6 may send and receive communication signals with a mobile terminal located inside the host vehicle 2. A terminal communication-type communication system 6 is, for example, at least one of a Bluetooth (registered trademark) device, a Wi-Fi (registered trademark) device, and an infrared communication device.

[0025] Map DB 7 stores map information usable in the driver assistance system 1. Map DB 7 is configured to include at least one type of non-transitory tangible storage medium, such as semiconductor memory, magnetic media, and optical media. Map DB 7 may also be a database for a locator that estimates the self-position of the host vehicle 2. Map DB 7 may also be a database for a navigation unit that navigates the driving route of the host vehicle 2. Map DB 7 may be constructed by a combination of multiple types of databases.

[0026] The map database 7 acquires and stores the latest map information, for example, through V2X communication with an external center via the communication system 6. The map information is digitized in two or three dimensions as information representing the external environment in which the host vehicle 2 is traveling. For three-dimensional map information, high-precision digital data may be used. The map information may include road information representing at least one type of information, such as the location, shape, size, and road surface condition of road structures.

[0027] Information display system 8 presents notification information to the occupants of the host vehicle 2, including the driver. Information display system 8 may also present notification information by stimulating the occupants' vision in the host vehicle 2. A visual information display type information display system 8 is at least one of the following: an in-vehicle monitor, a HUD (head-up display), a combination meter, and a navigation unit. Information display system 8 may also present notification information by stimulating the occupants' hearing. An auditory information display type information display system 8 is at least one of the following: a speaker and a buzzer.

[0028] The driver assistance system 1 is connected to the actuator system 4, sensor system 5, communication system 6, map DB 7, and information display system 8 via at least one of the following: LAN (local area network), wire harness, internal bus, and wireless communication line. The driver assistance system 1 is comprised of at least one dedicated computer.

[0029] The dedicated computer constituting the driver assistance system 1 may be a recognition ECU (electronic control unit) that controls the recognition of the external and internal environments as part of the driving control of the host vehicle 2. The dedicated computer constituting the driver assistance system 1 may be a locator ECU that estimates its own position in the driving control of the host vehicle 2. The dedicated computer constituting the driver assistance system 1 may be a planning ECU that plans the driving control of the host vehicle 2. The dedicated computer constituting the driver assistance system 1 may be a navigation ECU that navigates the driving route in the driving control of the host vehicle 2. The dedicated computer constituting the driver assistance system 1 may be an AD (autonomous driving) function and an ADAS (advanced driver assistance systems) function integrated as part of the driving control of the host vehicle 2.

[0030] The dedicated computer constituting the driver assistance system 1 may be an actuator ECU that controls the actuator system 4 as part of the driving control of the host vehicle 2. The dedicated computer constituting the driver assistance system 1 may be a motion domain ECU that integrates the control of multiple actuator ECUs as part of the driving control of the host vehicle 2. The dedicated computer constituting the driver assistance system 1 may be a central ECU that relays and / or mediates between multiple ECUs as part of the driving control of the host vehicle 2. The dedicated computer constituting the driver assistance system 1 may be at least one external computer that constructs, for example, an external center or mobile terminal that can communicate via the communication system 6.

[0031] The dedicated computer constituting the driver assistance system 1 has at least one memory 10 and one processor 12 as shown in Figure 1. The memory 10 is at least one type of non-transitory tangible storage medium, such as a semiconductor memory, magnetic medium, and optical medium, which non-temporarily stores programs and data that can be read by the computer. The processor 12 includes at least one type as a core, such as a CPU (central processing unit), GPU (graphics processing unit), and RISC (reduced instruction set computer)-CPU.

[0032] The processor 12 executes multiple instructions included in the driver assistance program stored as software in the memory 10. This allows the driver assistance system 1 to construct multiple functional blocks to assist in avoiding collisions with targets 3 during the driving of the host vehicle 2. These functional blocks constructed by the driver assistance system 1 include the recognition block 100, the planning block 120, and the control block 140 shown in Figure 3.

[0033] The recognition block 100 acquires sensing information from the sensor system 5. The recognition block 100 acquires communication information from the communication system 6. The recognition block 100 acquires map information from the map DB 7. The recognition block 100 acquires past information of control commands to the host vehicle 2 from the control block 140 by reading from the memory 10. The recognition block 100 processes this acquired information individually and then fuses it to recognize the state of the external and internal environments for each driving scene of the host vehicle 2 and generate recognition data.

[0034] Specifically, the recognition block 100 may generate recognition data by localization, which recognizes the self-state of the host vehicle 2, including its own position. The recognition data relating to the self-state may represent at least one of the following, such as position coordinates, velocity, acceleration, and yaw rate, which appear in the host vehicle 2 according to the control commands in the control block 140. The recognition block 100 may also generate recognition data by recognizing a target 3, including other road users, in the external environment of the host vehicle 2. The recognition data relating to the target 3 may represent at least one of the following, such as direction of travel, relative distance, relative velocity, relative acceleration, and collision margin time.

[0035] The recognition block 100 may generate recognition data by recognizing the road on which the host vehicle 2 is traveling. The recognition data relating to the road may represent at least one type of road structure, such as position, shape, size, and road surface condition. The recognition block 100 may also generate recognition data by recognizing the operations and / or states of the occupants, including the driver, in the host vehicle 2. In particular, the recognition data relating to operations for giving the host vehicle 2 a manual driving assistance task may represent at least one type, such as accelerator pedal operation amount, steering angle, steering torque, brake pedal operation amount, and shift position. Furthermore, the recognition data relating to operations for switching the driving task given to the host vehicle 2 between an automated driving task and a manual driving task may represent, for example, the operation state of a steering switch such as a changeover switch.

[0036] The planning block 120 acquires recognition data from the recognition block 100. The planning block 120 acquires past data of control commands to the host vehicle 2 by reading from the memory 10. Based on this acquired data, the planning block 120 plans the driving trajectory Td (see Figure 2), which will be the target track to follow in the future driving of the host vehicle 2. At this time, the driving trajectory Td is planned so as to define the time-series change of position coordinates for each control cycle, as the trajectory to follow the host vehicle 2 in future driving. The driving trajectory Td is further planned so as to directly or indirectly represent, through conversion calculations, at least one type of kinetic physical quantity from among, for example, velocity, acceleration, deceleration, yaw rate, and slip angle, as a motion parameter to appear at each control cycle on such a trajectory.

[0037] The control block 140 acquires recognition data from the recognition block 100. The control block 140 acquires data on the driving trajectory Td from the planning block 120. The control block 140 acquires past data of control commands to the host vehicle 2 by reading from the memory 10. Based on this acquired data, the control block 140 generates control commands to provide motion control, including attitude control, to the host vehicle 2. At this time, the control commands to the actuator system 4 are generated to perform driving control according to the level of automatic driving, which is adjusted according to the driving scene, among the automatic driving task and manual driving task in the host vehicle 2. The data of the control commands thus generated is stored in the memory 10.

[0038] Furthermore, in the above description, for example, the recognition block 100 and the planning block 120 may be implemented by a recognition ECU, and the control block 140 may be implemented by an actuator ECU. The recognition block 100 and the planning block 120 may be implemented by an ADAS domain ECU, and the control block 140 may be implemented by a motion domain ECU. The control block 140, along with the recognition block 100 and the planning block 120, may be implemented by a central ECU common to all of these blocks. Of course, each block 100, 120, and 140 may be implemented by configurations other than those exemplified above.

[0039] (Driving Assistance Flow) The driving assistance flow, which implements a driving assistance method to help avoid collisions with target 3 during the operation of the host vehicle 2, is repeatedly executed in accordance with Figure 6 by the joint efforts of the aforementioned blocks 100, 120, and 140 while the host vehicle 2 is running. In the following description, each "S" in the driving assistance flow refers to multiple steps executed by multiple commands included in the driving assistance program to help avoid collisions with target 3 during the operation of the host vehicle 2.

[0040] In S10 shown in Figure 6, the recognition block 100 determines whether the emergency braking conditions have been met for initiating collision avoidance with the target 3 during the host vehicle 2's future journey. The emergency braking conditions are met when the collision risk of the host vehicle 2 with the target 3 rises to within the emergency braking range, which requires the host vehicle 2 to perform emergency braking to avoid the collision. The rise in collision risk to within the emergency braking range is determined based on recognition data from the recognition block 100. At this time, the collision risk should be determined to have risen to within the emergency braking range if, for example, a dynamic target 3 such as a pedestrian shown in Figure 2 suddenly appears from a blind spot, requiring minimum risk operations such as deceleration beyond normal operation.

[0041] In S10 shown in Figure 6, if a negative judgment is made due to the failure to meet the emergency braking conditions, the current driver assistance flow ends. On the other hand, if a positive judgment is made in S10 due to the meeting of the emergency braking conditions, the current driver assistance flow proceeds to S20. In S20, the planning block 120 starts the avoidance control period Pc as shown in Figures 2 and 5 in order to control the braking posture of the host vehicle 2 in order to avoid a collision.

[0042] Following S20, in S30 shown in FIG. 6, the planning block 120 determines whether the emergency cooperation conditions for emergency cooperation avoidance of a collision with the target 3 in the future travel of the host vehicle 2 are satisfied. The emergency cooperation conditions are established when the collision risk of the host vehicle 2 with respect to the target 3 rises beyond the emergency braking range of S10 to within the emergency cooperation range where collision avoidance can be achieved by the cooperation of braking and steering for the host vehicle 2. The rise of the collision risk within the emergency cooperation range is determined based on the recognition data by the recognition block 100. At this time, it may be determined that the collision risk has reached within the emergency cooperation range when, within the collision margin time corresponding to the maximum deceleration achievable in the host vehicle 2, a situation is reached where a lateral movement amount for collision avoidance can be ensured.

[0043] In S30, when a negative determination is made due to the non - satisfaction of the emergency cooperation conditions, the current driving assistance flow shifts to S40. In S40, the planning block 120 plans the driving trajectory Td that is the following target of the host vehicle 2 over the emergency braking period Pci, which is before the establishment of the emergency cooperation conditions, among the avoidance control periods Pc shown in FIGS. 2 and 5. The driving trajectory Td in the emergency braking period Pci is planned to represent the time - series change of the position coordinates as a trajectory for collision avoidance by emergency braking.

[0044] In the emergency braking period Pci of S40, the driving trajectory Td is planned to give the time - series changes of the required longitudinal and lateral accelerations Gd shown in FIG. 5, the required yaw rate γd and the required slip angle βd shown in FIGS. 4 and 5, as the motion parameters required to follow such a trajectory. Note that the required longitudinal and lateral accelerations Gd are defined such that the backward direction opposite to the reference longitudinal direction X in the host vehicle 2 is the negative direction and the forward direction, which is the reference longitudinal direction X, is the positive direction (or the opposite direction relationship). Also, the required yaw rate γd and the required slip angle βd are defined such that the counter - clockwise direction around the yaw axis in the top - view of the host vehicle 2 is the positive direction and the clockwise direction is the negative direction (or the opposite direction relationship).

[0045] In S40, the planning block 120 sets the required yaw rate γd and required slip angle βd to be requested from the host vehicle 2 according to the driving trajectory Td, according to the road structure of the driving scene. Specifically, in S40, in the case of a driving scene on a straight road, the planning block 120 sets both the required yaw rate γd and the required slip angle βd to the zero value shown in Figure 5. On the other hand, in S40, in the case of a driving scene on a curved road, the planning block 120 sets the required yaw rate γd and the required slip angle βd to values ​​that match the curve structure of the curved road, such as the radius of curvature and / or cant condition. Here, the required yaw rate γd and / or required slip angle βd for a straight road may also be set to values ​​that match the cant condition, etc., similar to the curved road. Furthermore, in S40 when the host vehicle 2 is in a driver override state, not only the required slip angle βd but also the required yaw rate γd may be set to zero value regardless of the road structure during the emergency braking period Pci, and steering assistance may not be provided. Furthermore, straight roads and curved roads may be distinguished by a threshold value related to the radius of curvature. For example, the threshold is when the lateral acceleration is 1 m / s² for any given travel speed of the host vehicle 2. ２ It would be good to set the radius of curvature of the road to a degree that results in a certain degree of curvature.

[0046] Following S40, in S50 shown in Figure 6, the control block 140 controls the braking posture of the host vehicle 2 during the emergency braking period Pci so as to follow the driving trajectory Td planned in S40. The control block 140 then generates control commands for the braking actuator 44 to adjust the front wheel braking force Ff and the rear wheel braking force Fr during the emergency braking period Pci to emergency braking forces Ffi and Fri, respectively, according to the required longitudinal acceleration Gd shown in Figure 5.

[0047] Here, as time elapses from the start of the emergency braking period Pci, the magnitudes (i.e., absolute values) of the emergency braking forces Ffi and Fri may be increased and adjusted stepwise (as in the example of FIG. 5) or gradually (not shown). At this time, as the emergency braking forces Ffi and Fri are further increased beyond the increase value after the set time from the start of the adjustment, the driving trajectory Td in the emergency coordination period Pce, which will be described in detail later, may be planned in advance in a planned pattern for the rapid start of the emergency coordination period Pce.

[0048] In S50, further, in the case of a driving scene on a straight road, the control block 140 generates a control command for the steering actuator 42 according to the required yaw rate γd and the required slip angle βd, both of which are set to zero values by S40. At this time, the control command is set so as to adjust the front wheel steering angle δf and the rear wheel steering angle δr to 0° corresponding to both the required yaw rate γd and the required slip angle βd shown in FIG. 5 during the emergency braking period Pci. As a result, the host vehicle 2 is controlled to a braking posture in which the actual yaw rate γa and the actual slip angle βa shown in FIG. 4 are aligned with the straight road for collision avoidance within the emergency braking period Pci.

[0049] On the other hand, in S50, in the case of a driving scene on a curved road, the control block 140 generates a control command for the steering actuator 42 according to the required yaw rate γd and the required slip angle βd set according to the curve structure of the curved road by S40. At this time, the control command is set so as to adjust the front wheel steering angle δf and the rear wheel steering angle δr to an inverse phase angle, a same phase angle, or 0° corresponding to both the required yaw rate γd and the required slip angle βd, respectively, during the emergency braking period Pci. As a result, the host vehicle 2 is controlled to a braking posture in which the actual yaw rate γa and the actual slip angle βa are aligned with the curved road for collision avoidance within the emergency braking period Pci.

[0050] Following S50, in S60 shown in Figure 6, the control block 140 determines whether or not the emergency braking condition has been resolved in the current driving support flow. If the result is positive due to the resolution of the emergency braking condition, the current driving support flow ends. On the other hand, as long as the result is negative due to the remaining emergency braking condition, the current driving support flow returns to S30, the next control cycle as the emergency braking period Pci begins, and the process of determining whether the emergency coordination condition has been met is repeated.

[0051] In the repeated S30, if an affirmative judgment is made due to the fulfillment of the emergency coordination conditions, the current driving support flow proceeds to S70. In S70, the planning block 120 plans the driving trajectory Td that will be the target follow for the host vehicle 2 during the emergency coordination period Pce, which is after the fulfillment of the emergency coordination conditions, within the avoidance control period Pc shown in Figures 2 and 5. The driving trajectory Td during the emergency coordination period Pce is planned to represent the time-series change of position coordinates as a trajectory for collision avoidance through the coordination of braking and steering.

[0052] During the emergency coordination period Pce in S70, the driving trajectory Td is planned to provide the time-series changes of the required longitudinal acceleration Gd shown in Figure 5, and the required yaw rate γd and required slip angle βd shown in Figures 4 and 5, as motion parameters required according to that trajectory. In particular, the required slip angle βd shown in Figures 4 and 5 is given by the following equation 1, using the required lateral velocity Vyd required in the lateral direction of the host vehicle 2 according to the trajectory during the emergency coordination period Pce, and the actual longitudinal velocity Vxa of the host vehicle 2 represented in the longitudinal direction by the recognition data from the recognition block 100.

[0053] Here, the required slip angle βd in equation 1 is preferably given in accordance with the required lateral speed Vyd, which follows the trajectory of the emergency coordination period Pce, within a range less than or equal to the maximum lateral speed estimated to be achievable in the current host vehicle 2. Along with this, or instead, the required slip angle βd may be given within a range less than or equal to the maximum slip angle estimated to be achievable in the current host vehicle 2. The required lateral speed Vyd is defined such that the left direction is set as the positive direction and the right direction as the negative direction (or the exact opposite direction) in the left-right direction of the host vehicle 2. Furthermore, the maximum lateral speed that determines the setting range of the required lateral speed Vyd is preferably estimated according to at least one of the following in the current host vehicle 2: the state of the steering actuator 42 for the rear wheels 20rl, 20rr, the maximum steering angle, and the maximum steering angular velocity.

[0054] In this S70 scenario, when driving on a straight road, the planning block 120 sets the required slip angle βd, which it requests from the host vehicle 2 according to the driving trajectory Td, to a value that generates a lateral movement effective for collision avoidance, as shown in Figure 5. However, even in the S70 scenario when driving on a straight road, the planning block 120 forces the required yaw rate γd, which it requests from the host vehicle 2 according to the driving trajectory Td, to the zero value shown in Figure 5.

[0055] In S70, on the other hand, in the case of a driving scene on a curved road, the planning block 120 sets the required slip angle βd that it requests from the host vehicle 2 according to the driving trajectory Td to a value that matches the curve structure of the curved road while producing a lateral movement amount effective for collision avoidance. However, even in S70, which is the case of a driving scene on a curved road, the planning block 120 sets the required yaw rate γd that it requests from the host vehicle 2 according to the driving trajectory Td to a value that matches the curve structure of the curved road, such as the radius of curvature and / or cant state. In other words, the setting value of the required yaw rate γd on a curved road is forced to zero for the component value that produces a lateral movement amount effective for collision avoidance, and is limited to a component value that matches the curve structure. Here, the required yaw rate γd and / or required slip angle βd on a straight road may also be set to a value that matches the cant state, etc., in the same way as on a curved road.

[0056] Following S70, in S80 shown in Figure 6, the control block 140 controls the braking posture of the host vehicle 2 during the emergency coordination period Pce so as to follow the driving trajectory Td planned in S70. The control block 140 then generates control commands for the braking actuator 44 to adjust the front wheel braking force Ff and the rear wheel braking force Fr during the emergency coordination period Pce to emergency coordination braking forces Ffe and Fre, respectively, according to the required longitudinal acceleration Gd shown in Figure 5.

[0057] In S80, the control block 140 further generates control commands for the steering actuator 42 according to the required yaw rate γd and required slip angle βd set in S70 according to the road structure of the driving scene. At this time, the control commands are set to adjust the front wheel steering angle δf and rear wheel steering angle δr during the emergency coordination period Pce to in-phase angles that correlate with both the required yaw rate γd and the required slip angle βd shown in Figure 5. Thus, the front wheel steering angle δf and rear wheel steering angle δr that correlate with both the required yaw rate γd and the required slip angle βd are given by the following equations 2 to 7.

[0058] Here, in equations 2 and 3 described above, Gγf is a steady-state gain for controlling the amount of adjustment of the front wheel steering angle δf with respect to the required yaw rate γd. Gγr in equations 2 and 4 is a steady-state gain for controlling the amount of adjustment of the rear wheel steering angle δr with respect to the required yaw rate γd. Gβf in equations 2 and 5 is a steady-state gain for controlling the amount of adjustment of the front wheel steering angle δf with respect to the required slip angle βd. Gβr in equations 2 and 6 is a steady-state gain for controlling the amount of adjustment of the rear wheel steering angle δr with respect to the required slip angle βd. Note that when determining the steering angles δf and δr from the required yaw rate γd and the required slip angle βd, the transfer function showing the transient response of the vehicle derived from the equations of motion of the two-wheel model may be used.

[0059] Furthermore, in equations 3 to 7 described above, A is the stability factor representing the steering characteristics of the host vehicle 2. V in equations 3 to 6 may be the actual longitudinal speed Vxa of the host vehicle 2. V in equations 3 to 6 may be the combined speed of the actual lateral speed Vya (see Figure 4) and the actual longitudinal speed Vxa of the host vehicle 2. V in equations 3 to 6 may be the combined speed of the required lateral speed Vyd and the actual longitudinal speed Vxa of the host vehicle 2. l in equations 3 to 7 is the wheelbase between the axes of the front wheel sections 20fl, 20fr and the rear wheel sections 20rl, 20rr of the host vehicle 2. lf in equations 5 to 7 is the longitudinal distance between the center of gravity of the host vehicle 2 and the axes of the front wheel sections 20fl, 20fr of the host vehicle 2, within the wheelbase l. lr in equations 5 to 7 is the longitudinal distance between the center of gravity of the host vehicle 2 and the axes of the rear wheel sections 20rl, 20rr of the host vehicle 2. In equations 5-7, m represents the mass of the host vehicle 2. In equations 6 and 7, Kf represents the cornering power of the tires at the front wheel sections 20fl and 20fr. In equations 5 and 7, Kr represents the cornering power of the tires at the rear wheel sections 20rr and 20rr.

[0060] In S80 based on such numbers 2 to 7, the control block 140 may estimate the ground contact load during the emergency coordination period Pce based, for example, on the control command to the actuator system 4 and the transient response characteristics of the host vehicle 2. In this case, the cornering power Kf and / or Kr may be increased or decreased in accordance with the estimated ground contact load for at least one of the front wheel sections 20fl, 20fr and the rear wheel sections 20rl, 20rr. As a result of the increase or decrease, the control command will be set to correct and adjust at least one of the front wheel steering angle δf and the rear wheel steering angle δr in accordance with the fluctuation in ground contact load.

[0061] In this S80, the actual steering angles of the front wheel steering angle δf and rear wheel steering angle δr, which are requested by the control command for in-phase adjustment, are servo-controlled by the steering actuator 42. On the other hand, outside of the avoidance control period Pc, in the servo control of the steering actuator 42 during the steady-state control period Ps shown in Figure 7, a limit is usually set on the rear wheel steering angle δr to ensure turning stability. This limit on the rear wheel steering angle δr is achieved by setting the magnitude (i.e., absolute value) of at least one of the steering angle upper limit value δrt and angular velocity upper limit value ωrt shown in Figure 7 to be smaller than the front wheel steering angle δf.

[0062] Therefore, in S80, during the emergency coordination period Pce, in particular within the avoidance control period Pc, when the required steering angle δrd of the rear wheel steering angle δr is set to increase, the control block 140 generates a control command to the steering actuator 42 to release the restriction and secure the actual steering angle δra of the rear wheel steering angle δr. The servo control by the steering actuator 42 that receives the control command is preferably realized by parallelizing feedforward control based on the deviation of the actual steering angle δra from the required steering angle δrd and feedback control based on said deviation.

[0063] As a result of S80, the host vehicle 2 is controlled to a braking posture that matches the road structure, with the actual yaw rate γa and actual slip angle βa shown in Figure 4, in order to avoid a collision within the emergency coordination period Pce. In particular, in S80, the current requested yaw rate γd set in S70 may be feedback-corrected based on the deviation of the actual yaw rate γa from the past requested yaw rate γd, and then used to set control commands to adjust the steering angles δf and δr in phase according to equations 2 to 7. In this case, it becomes possible to improve the responsiveness of the actual yaw rate γa to the requested yaw rate γd and achieve collision avoidance within the shortest possible emergency coordination period Pce.

[0064] Furthermore, in S80 when the host vehicle 2 is in an override state by the driver, the requested yaw rate γd set in S70 may be corrected to match the driver's steering angle and then used to set control commands to adjust the steering angles δf and δr in phase according to equations 2 to 7. In this case, in addition to the servo control described above that follows the set control commands, torque assist control may be performed in the steering actuator 42 to assist the reaction torque to the driver's steering.

[0065] Following S80, in S90 shown in Figure 6, the control block 140 determines whether or not the emergency coordination condition has been resolved in the current driving support flow. As long as the result is negative due to the emergency coordination condition not being resolved, the current driving support flow returns to S70, the next control cycle as the emergency coordination period Pce begins, and the attitude control processing in the emergency coordination period Pce is continuously repeated. On the other hand, if collision avoidance is achieved by resolving the emergency coordination condition and a positive determination is made, the current driving support flow ends. In addition, depending on the operating state of the steering actuators 42 for the rear wheels 20rl, 20rr, for example, if it is determined that reverse-phase adjustment of the steering angles δf, δr is optimal rather than in-phase adjustment, the determination of the resolution of the emergency coordination condition by S90 may be performed with the reverse-phase adjustment prioritized by S80.

[0066] (Effects) The effects of the first embodiment described above are explained below.

[0067] According to the first embodiment, the front wheel steering angle δf and rear wheel steering angle δr, respectively, applied by the steering actuator 42 to the front wheel sections 20fl, 20fr and rear wheel sections 20rl, 20rr in the host vehicle 2, are adjusted in phase with respect to the reference longitudinal direction X. As a result, during the avoidance control period Pc (particularly the emergency coordination period Pce in the embodiment) aimed at avoiding a collision with the target 3 in the host vehicle 2, the braking posture of the host vehicle 2 can be transitioned to the direction of travel Dd in which each section 20fl, 20fr, 20rl, 20rr rolls, as shown in Figure 4, according to the planned driving trajectory Td. Therefore, it becomes possible to secure an effective amount of lateral movement for collision avoidance in the host vehicle 2.

[0068] According to the first embodiment, the front wheel steering angle δf and the rear wheel steering angle δr are correlated and adjusted to both the required yaw rate γd and the required slip angle βd, which are required according to the driving trajectory Td during the avoidance control period Pc. As a result, in a host vehicle 2 where the braking posture of the front wheel sections 20fl, 20fr and the rear wheel sections 20rl, 20rr transitions to the direction of travel Dd and a lateral movement amount can be secured, it becomes possible to accurately generate the actual yaw rate γa and actual slip angle βa that are effective for collision avoidance.

[0069] According to the first embodiment, the front wheel steering angle δf and the rear wheel steering angle δr are correlated and adjusted to both the required yaw rate γd required around the yaw axis of the host vehicle 2 for collision avoidance during the avoidance control period Pc, and the required slip angle βd corresponding to the required lateral velocity Vyd required laterally for the host vehicle 2 for said avoidance. As a result, in a host vehicle 2 in which the braking posture of the front wheel sections 20fl, 20fr and the rear wheel sections 20rl, 20rr transitions to the direction of travel Dd and a lateral movement amount can be secured, it becomes possible to effectively manifest the actual slip angle βa corresponding to the actual lateral velocity Vya, along with the actual yaw rate γa, for collision avoidance.

[0070] According to the first embodiment, even if a restriction is normally set on the rear wheel steering angle δr during the steady-state control period Ps outside the avoidance control period Pc to ensure the turning stability of the host vehicle 2, this restriction is released during the avoidance control period Pc. This makes it possible to secure the rear wheel steering angle δr, which is adjusted in phase with the front wheel steering angle δf, at an angle effective for collision avoidance, thereby generating an actual yaw rate γa and actual slip angle βa suitable for the host vehicle 2 during the avoidance control period Pc.

[0071] According to the first embodiment, at least one of the front wheel steering angle δf and the rear wheel steering angle δr is corrected in accordance with the fluctuations in the ground contact load estimated during the avoidance control period Pc. This makes it possible to effectively correct at least one of the in-phase adjusted front wheel steering angle δf and rear wheel steering angle δr, where fluctuations in the ground contact load can be a factor in the adjustment error, in order to avoid a collision. Therefore, it becomes possible to produce an actual yaw rate γa and an actual slip angle βa suitable for the avoidance control period Pc in the host vehicle 2, regardless of the time-changing ground contact state.

[0072] (Second Embodiment) The second embodiment is a modification of the first embodiment. In the driving support flow of the second embodiment shown in Figure 8, S280 is executed instead of S80.

[0073] In S280, the control block 140 generates a control command to the steering actuator 42 in the servo control of at least the front wheel steering angle δf, of the front wheel steering angle δf and the rear wheel steering angle δr, so as to correct the self-aligning torque that decreases and fluctuates during the emergency coordination period Pce. This is because, due to the in-phase adjustment of the steering angles δf and δr, the actual yaw rate γa decreases compared to the case of out-of-phase adjustment, resulting in a generally greater mechanical friction force at the rear wheel section 20rl and 20rr than at the front wheel section 20fl and 20fr, and thus the effect of fluctuations in self-aligning torque on the torque required for steering is greater at the front wheel section 20fl and 20fr than at the rear wheel section 20rl and 20rr.

[0074] The servo control by the steering actuator 42, upon receiving a control command, should reduce the control gain of the feedforward control with respect to the required steering angle δrd compared to the steady-state control period Ps, at least in accordance with the decrease in the self-aligning torque of the front wheels 20fl and 20fr. Furthermore, such correction in accordance with fluctuations in self-aligning torque may also be performed in the torque assist control by the steering actuator 42. Aside from the points mentioned above, the same processing as in S80 of the first embodiment is performed in S280.

[0075] According to this second embodiment, at least the front wheel steering angle δf is corrected in accordance with the fluctuations in the self-aligning torque estimated during the avoidance control period Pc, compared to the front wheel steering angle δf and the rear wheel steering angle δr. This makes it possible to effectively correct at least the front wheel steering angle δf, which is among the steering angles adjusted in phase and which can become a source of adjustment errors such as overshoot due to fluctuations in the self-aligning torque, in order to avoid a collision. Therefore, it becomes possible to produce an actual yaw rate γa and an actual slip angle βa suitable for the avoidance control period Pc, regardless of the time-varying steering characteristics of the host vehicle 2.

[0076] (Third Embodiment) The third embodiment is a modification of the first embodiment. In the driving support flow of the third embodiment shown in Figure 9, S380 is executed instead of S80.

[0077] In S380, the control block 140 generates a control command for the braking actuator 44 to adjust at least one of the emergency coordinated braking forces Ffe and Fre during the transient period Pcet in which the steering angles δf and δr change over time, as shown in Figure 10, within the avoidance control period Pc. This control command addresses concerns about unstable behavior in the host vehicle 2, where lateral forces are generated as a result of the time change in the steering angles δf and δr, which are adjusted in phase, making it easier for slip relative to the emergency coordinated braking forces Ffe and Fre to be amplified in the longitudinal direction.

[0078] Therefore, the control command to the braking actuator 44 is set so that the required slip ratio Rx during the transient period Pcet shown in Figure 10 is limited more than the stabilization period Pceb during the avoidance control period Pc, in which the steering angles δf and δr are stabilized. In the ABS control by the braking actuator 44 that receives the control command, the magnitude (i.e., absolute value) of at least one of the emergency coordinated braking forces Ffe and Fre, which is necessary to achieve the limited required slip ratio Rx, is adjusted to be reduced in the transient period Pcet compared to the stabilization period Pceb. Alternatively, the limitation of the required slip ratio Rx may be achieved by limiting the wheel rotation speed or the vehicle's longitudinal speed at the wheel position according to the slip ratio.

[0079] Thus, the braking force adjustment according to the required slip ratio Rx limited by S380 may be implemented not only during the transient period Pceet but also during the stabilization period Pceb and / or the emergency braking period Pci in the case of driving on a curved road. Aside from the points mentioned above, S380 performs the same processing as S80 in the first embodiment.

[0080] According to this third embodiment, the emergency coordinated braking force Ffe and / or Fre applied from the braking actuator 44 to at least one of the front wheel sections 20fl, 20fr and the rear wheel sections 20rl, 20rr in the host vehicle 2 is adjusted during the transient period Pcet in which the steering angles δf and δr change over time within the avoidance control period Pc. As a result, even during the transient period Pcet in which the generation of lateral forces is a concern due to the time change of the in-phase adjusted front wheel steering angle δf and rear wheel steering angle δr, the host vehicle 2 can limit the required slip ratio Rx for the emergency coordinated braking force Ffe and Fre. Consequently, a host vehicle 2 capable of stabilizing its behavior makes it easier to secure a lateral movement amount effective for collision avoidance.

[0081] (Other Embodiments) Although several embodiments have been described above, this disclosure is not to be construed as being limited to those embodiments, and can be applied to various embodiments and combinations without departing from the spirit of this disclosure.

[0082] In the modified example, the dedicated computer constituting the driver assistance system 1 may have at least one of the digital circuit and the analog circuit as a processor. Here, the digital circuit is at least one of the following, for example, ASIC (application specific integrated circuit), FPGA (field programmable gate array), SOC (system on a chip), PGA (programmable gate array), and CPLD (complex programmable logic device). Furthermore, such a digital circuit may have a memory that stores a program.

[0083] In modified versions, attitude control during the emergency braking period Pci may be omitted by skipping S10, S20, and S40-S60. In modified versions, S280 of the second embodiment and S380 of the third embodiment may be combined and executed. In modified versions, the operator who manually drives the host vehicle 2 to which the driver assistance system 1 is applied may be a remote operator who remotely controls the driving of the host vehicle 2 from an external center. In modified versions, the driver assistance system 1 may be configured to be achievable only for automated driving tasks, without the existence of manual driving assistance tasks to support the operator's manual driving operations.

[0084] (Addendum) This specification discloses several technical ideas and several combinations thereof, as listed below. The symbols in parentheses in this addendum indicate the correspondence with the specific means described in the embodiments detailed above, and do not limit the technical scope of this disclosure.

[0085] (Technical Concept 1) A driving assistance system having at least one processor (12) to assist in avoiding a collision with a target (3) while driving a host vehicle (2), wherein the at least one processor is configured to plan the driving trajectory (Td) of the host vehicle and to control the braking posture of the host vehicle during the avoidance control period (Pc) toward collision avoidance by adjusting the front wheel steering angle (δf) and rear wheel steering angle (δr) applied to the front wheel section (20fl, 20fr) and rear wheel section (20rl, 20rr) respectively by steering actuators (42) in phase with respect to the reference longitudinal direction (X).

[0086] (Technical Concept 2) The driving support system according to Technical Concept 1, wherein controlling the braking posture includes adjusting the in-phase front wheel steering angle and the rear wheel steering angle, which are correlated with both the required yaw rate (γd) and the required slip angle (βd) required according to the driving trajectory during the avoidance control period.

[0087] (Technical Concept 3) A driving assistance system according to Technical Concept 2, wherein controlling the braking posture involves adjusting the in-phase front wheel steering angle and the rear wheel steering angle, which are correlated with both the required yaw rate required around the yaw axis of the host vehicle for collision avoidance during the avoidance control period and the required slip angle corresponding to the required lateral velocity (Vyd) required laterally of the host vehicle for collision avoidance during the avoidance control period.

[0088] (Technical Concept 4) A driving assistance system according to any one of Technical Concepts 1 to 3, wherein controlling the braking posture includes releasing the restriction set on the rear wheel steering angle during the steady-state control period (Ps) outside the avoidance control period during the avoidance control period.

[0089] (Technical Concept 5) A driving assistance system according to any one of Technical Concepts 1 to 4, wherein controlling the braking posture includes correcting at least one of the front wheel steering angle and the rear wheel steering angle in accordance with the fluctuations in ground contact load estimated during the avoidance control period.

[0090] (Technical Concept 6) A driving assistance system according to any one of Technical Concepts 1 to 5, wherein controlling the braking posture includes correcting at least the front wheel steering angle among the front wheel steering angle and the rear wheel steering angle in accordance with fluctuations in the self-aligning torque estimated during the avoidance control period.

[0091] (Technical Concept 7) A driving assistance system according to any one of Technical Concepts 1 to 6, wherein controlling the braking posture includes limiting the slip ratio (Rx) with respect to the braking force by adjusting the braking force (Ffe, Fre) applied from a braking actuator (44) to at least one of the front wheel section and the rear wheel section of the host vehicle during a transient period (Pcet) in which the front wheel steering angle and the rear wheel steering angle change over time during the avoidance control period.

[0092] Furthermore, the technical concepts 1 to 7 described above may also be understood within the respective technical concepts of the methods and programs.

Claims

1. A driving assistance system having at least one processor (12) to assist in avoiding a collision with a target (3) while driving a host vehicle (2), wherein the at least one processor is configured to plan the driving trajectory (Td) of the host vehicle and to control the braking posture of the host vehicle during the avoidance control period (Pc) toward collision avoidance by adjusting the front wheel steering angle (δf) and rear wheel steering angle (δr) applied by steering actuators (42) to the front wheel section (20fl, 20fr) and rear wheel section (20rl, 20rr) of the host vehicle in phase with respect to the reference longitudinal direction (X).

2. The driving assistance system according to claim 1, wherein controlling the braking posture includes adjusting the in-phase front wheel steering angle and the rear wheel steering angle, which are correlated with both the required yaw rate (γd) and the required slip angle (βd) required according to the driving trajectory during the avoidance control period.

3. The driving assistance system according to claim 2, wherein controlling the braking posture includes adjusting the in-phase front wheel steering angle and the rear wheel steering angle, which are correlated with both the required yaw rate required around the yaw axis of the host vehicle for collision avoidance during the avoidance control period and the required slip angle corresponding to the required lateral velocity (Vyd) required laterally of the host vehicle for collision avoidance during the avoidance control period.

4. The driving assistance system according to claim 1 or 2, wherein controlling the braking posture includes releasing the restriction set on the rear wheel steering angle during the steady-state control period (Ps) outside the avoidance control period during the avoidance control period.

5. The driving assistance system according to claim 1 or 2, wherein controlling the braking posture includes correcting at least one of the front wheel steering angle and the rear wheel steering angle in accordance with the fluctuations in ground contact load estimated during the avoidance control period.

6. The driving assistance system according to claim 1 or 2, wherein controlling the braking posture includes correcting at least the front wheel steering angle among the front wheel steering angle and the rear wheel steering angle in accordance with fluctuations in the self-aligning torque estimated during the avoidance control period.

7. The driving assistance system according to claim 1 or 2, wherein controlling the braking posture includes limiting the slip ratio (Rx) with respect to the braking force by adjusting the braking force (Ffe, Fre) applied from the braking actuator (44) to at least one of the front wheel portion and the rear wheel portion of the host vehicle during a transient period (Pcet) in which the front wheel steering angle and the rear wheel steering angle change over time during the avoidance control period.

8. A driving assistance method performed by at least one processor (12) to assist in avoiding a collision with a target (3) during the operation of a host vehicle (2), the method comprising: planning the driving trajectory (Td) of the host vehicle; and controlling the braking posture of the host vehicle during the avoidance control period (Pc) toward collision avoidance by adjusting the front wheel steering angle (δf) and rear wheel steering angle (δr) applied to the front wheel section (20fl, 20fr) and rear wheel section (20rl, 20rr) respectively by steering actuators (42) in phase with respect to a reference longitudinal direction (X).

9. A driving assistance program stored in at least one storage medium (10) to assist in avoiding a collision with a target (3) during the operation of a host vehicle (2), and including instructions for causing at least one processor (12) to perform the collision avoidance assistance, the program including instructions for planning the driving trajectory (Td) of the host vehicle, and controlling the braking posture of the host vehicle during the avoidance control period (Pc) toward collision avoidance by adjusting the front wheel steering angle (δf) and rear wheel steering angle (δr) applied by steering actuators (42) to the front wheel section (20fl, 20fr) and rear wheel section (20rl, 20rr) of the host vehicle in phase with respect to a reference longitudinal direction (X).

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